Plasma processing systems are commonly used for modifying the surface properties of substrates in various industrial applications. For example, plasma processing systems are routinely used to plasma treat the surfaces of integrated circuits, electronic packages, and printed circuit boards in semiconductor applications, solar panels, hydrogen fuel cell components, automotive components, and rectangular glass substrates used in flat panel displays. Often, the substrates that are subjected to plasma processing have the geometrical form factor or shape of rectangular strips with opposite side edges that are substantially parallel.
Conventional plasma processing systems include a plasma chamber and a material handling system that transfers substrates to a processing space inside the plasma chamber for plasma treatment. Traditionally, electrodes inside the plasma chamber of an in-line plasma processing system have included rails used to support the transferred strips during plasma treatment. The rails are supplied in parallel pairs that are ideally aligned with corresponding rails on the material handling system. The rails inside the plasma processing system have a separation selected such that the rails contact side edges of each strip loaded from the material handling system onto the rails.
In one conventional electrode design, the substrate-supporting rails are formed integrally with the rest of the electrode. If the plasma processing system is retooled to plasma treat strips having a different width between the contacted side edges, the entire electrode must be replaced with a different electrode having integral rails with a different relative separation. This results in lost production time for replacing the electrode. Moreover, the integral rails on the new electrode may be misaligned with the rails on the material handling system, which is impossible to remedy with an adjustment to the electrode rails because of their integral construction.
To overcome this deficiency, plasma processing system manufacturers have introduced electrode assemblies with non-integral rails that are movable among multiple different separations across the surface of an electrode. This conventional rail construction features guide bars and rails with set screws that are loosened to change the separation between the rails constrained by the guide bars and tightened to fix the separation between the rails. Typically, an operator will make fiduciary marks on the electrode for use in aligning the rails to accept strips of different widths. However, aligning the rails with fiduciary marks to fix the rail positions is not readily reproducible, especially among multiple different operators, due in large part to the subjectivity involved in aligning the rails with the fiduciary marks. Moreover, the set screws must be loosened and tightened in order to change the distance between adjacent rails, which requires tools and slows the process. Productivity is lost during the time required to loosen each rail, align the rails with a set of fiduciary marks, and then tighten each rail without inadvertently altering the alignment.
It would be desirable, therefore, to provide an electrode construction for a plasma processing system that overcomes these and other deficiencies of conventional electrode constructions.